Irenaeus was born during the first half of the 2nd century (the exact date is disputed: between the years 115 and 125 according to some, or 130 and 142 according to others), and he is thought to have been a Greek from Polycarp’s hometown of Smyrna in Asia Minor, now İzmir, Turkey. Unlike many of his contemporaries, he was brought up in a Christian family rather than converting as an adult.
During the persecution of Marcus Aurelius, the Roman Emperor from 161–180, Irenaeus was a priest of the Church of Lyon. The clergy of that city, many of whom were suffering imprisonment for the faith, sent him in 177 to Rome with a letter to Pope Eleutherius concerning the heresy Montanism, and that occasion bore emphatic testimony to his merits. While Irenaeus was in Rome, a persecution took place in Lyon. Returning to Gaul, Irenaeus succeeded the martyr Saint Pothinus and became the second Bishop of Lyon.
During the religious peace which followed the persecution of Marcus Aurelius, the new bishop divided his activities between the duties of a pastor and of a missionary (as to which we have but brief data, late and not very certain). Almost all his writings were directed against Gnosticism. The most famous of these writings is Adversus haereses (Against Heresies). Irenaeus alludes to coming across Gnostic writings, and holding conversations with Gnostics, and this may have taken place in Asia Minor or in Rome. However, it also appears that Gnosticism was present near Lyon: he writes that there were followers of ‘Marcus the Magician’ living and teaching in the Rhone valley.
As bishop, Irenaeus saw himself as a successor of the apostles; a link between the historical person of Jesus and the contemporary Church. Like St. Ignatius of Antioch, Irenaeus saw himself as the centre of the Eucharist however he also saw himself as a teacher. Because of his confrontation with the Gnostics, Irenaeus placed appropriate importance to the continuity of teaching within the Church. (10) Since the Gnostics appealed to a secret tradition handed down by a secret succession of pedagogues, Irenaeus answered by appealing to the tradition openly promulgated in the four canonical gospels and to the unbroken public succession of bishops within a see. He saw himself as the one, par excellence, who taught the truth.
“We should obey those presbyters in the Church who have their succession from the apostles, and who, together with succession in the episcopate, have received the assured charisma of the truth (certum charisma veritatis).”
Irenaeus viewed apostolic succession as the true sign of continuity with the apostolic faith. He saw himself as a successor of the apostles, as alter apostolus and therefore as someone who preserved the continuity of doctrinal teaching, the fullness of the Catholic faith and life.
The last action reported of him (by Eusebius, 150 years later) is that in 190 or 191, he exerted influence on Pope Victor I not to excommunicate the Christian communities of Asia Minor which persevered in the practice of the Quartodeciman celebration of Easter. Eusebius the historian relates that Irenaeus lived up to his name as ‘peacemaker.’ “Irenaeus, whose name means ‘peaceable’ and who by temperate was a peacemaker, pleaded and negotiated thus for the peace of the churches. He corresponded by letter not only with Victor but with very many other heads of churches, setting out both sides of the question under discussion.”
Like those of his birth and early life in Asia Minor, nothing is known of the date of his death, which must have occurred at the end of the 2nd or the beginning of the 3rd century. A few within the Roman Catholic Church and Orthodox Church celebrate him as a martyr. He was buried under the Church of Saint John in Lyon, which was later renamed Saint Irenaeus in his honour. The tomb and his remains were utterly destroyed in 1562 by the Huguenots.